The present invention relates to a limiter circuit capable of blocking output current from flowing until input supply voltage reaches a predetermined value.
FIGS. 1 and 2 show examples of conventional limiter circuit each comprising a diode. The limiter circuit shown in FIG. 1 comprises a resistor 1 to one end of which is supplied positive input voltage +Vi, a resistor 2 to one end of which is supplied negative reference voltage -e, and a diode 3 whose anode is connected to the other ends of resistors 1 and 2, respectively, and whose cathode is connected to the ground potential point. On the other hand, the limiter circuit shown in FIG. 2 comprises a resistor 1 to one end of which is supplied negative input voltage -Vi, a resistor 2 to one end of which is supplied positive reference voltage +e, and a diode 3 whose cathode is connected to the other ends of resistors 1 and 2, respectively, and whose anode is connected to the ground potential point. FIGS. 3 and 4 show characteristic curves of the relation between input voltage Vi and output current I of the limiter circuits shown in FIGS. 1 and 2, respectively. Input voltage is plotted on the abscissa and output current I on the ordinate. As is apparent from FIGS. 3 and 4, output current I does not flow when input voltage Vi (absolute value) is small, but starts to flow only when input voltage Vi reaches e.R.sub.1 /R.sub.2 (in the case of circuit shown in FIG. 1) and -e.R.sub.1 /R.sub.2 (in the case of circuit shown in FIG. 2). Thereafter, as input voltage Vi (absolute value) increases, output current I also increases at the slope of 1/R.sub.1. R.sub.1 and R.sub.2 represent the resistance values of resistors 1 and 2, respectively.
As described above, the circuits shown in FIGS. 1 and 2 serve to block current from flowing until input voltage Vi comes to predetermined values (e.R.sub.1 /R.sub.2) in the case of circuit shown in FIG. 1 and (-e.R.sub.1 /R.sub.2) in the case of circuit shown in FIG. 2. In short, these circuits serve to function as a limiter circuit.
However, the conventional limiter circuits shown in FIGS. 1 and 2 have disadvantages in that a reference voltage having a polarity reverse to that of the input voltage is needed and in that a current buffer circuit must be arranged between the diode and the ground potential point to take out output current since the diode is connected to the ground potential point.